Gas turbine engines operate to produce mechanical work or thrust. Specifically, land-based gas turbine engines typically have a generator coupled thereto for the purposes of generating electricity. A gas turbine engine comprises an inlet that directs air to a compressor section, which has stages of rotating compressor blades. As the air passes through the compressor, the air pressure increases. The compressed air is then directed into one or more combustors where fuel is injected into the compressed air and the mixture is ignited. The hot combustion gases are then directed from the combustion section to a turbine section by a transition duct. The hot combustion gases cause the stages of the turbine to rotate, which in turn, causes the compressor to rotate.
The air and hot combustion gases are directed through a turbine section by turbine blades and vanes. These blades and vanes are subject to extremely high operating temperatures, often times upwards of 2500 deg. F. These temperatures often exceed the material capability from which the blades and vanes are made. In order to lower the effective operating temperature, the blades and vanes are cooled, often with air or steam. However, cooling hole geometry can also lead to areas of high stress. One such area of high stress is in a platform region of a turbine blade and vane. In prior art turbine blade/vane designs, the air passes through the platform by a series of round cooling holes. However, the blade/vane undergoes large variations in thermal gradients resulting in large thermal stresses. These stresses are actually compounded by the presence of the cooling holes, while providing cooling air to the region, have been found to be sources of stress risers. As a result, cracking has been known to occur in and around the cooling holes.